The present invention relates to a vacuum interrupter, and more particularly to a vacuum interrupter wherein a bellows maintains air-tightness of a vacuum vessel.
Generally, a vacuum interrupter comprises a pair of electrical contacts disposed so that one is in contact with the other or away therefrom through a pair of contact rods extending into a vacuum vessel so that one is close to the other or away therefrom. To move the contact rod positioned on a movable side while maintaining air-tightness within the vacuum vessel, the vacuum interrupter further comprises a bellows, one end of which is hermetically joined to the movable contact rod while the other end is hermetically joined to the vacuum vessel.
However, when each member constituting the above interrupter is provisionally assembled under the condition that brazing material is interposed therebetween, the following drawbacks are pointed out:
First, it is difficult to effect positioning of the bellows in both axial and radial directions with respect to the vacuum vessel.
Second, it is difficult to effect positioning of the brazing material interposed between the bellows and the vacuum vessel.
Specifically, where the vacuum vessel comprises a metallic casing member and an insulating end plate fastened to the opening end of the metallic casing member, elimination of the above mentioned drawbacks is required.
That is, the insulating end plate is provided with a bore in the center thereof, and metallized layers provided on the side of inner radius and on the side of outer radius. Assuming that the insulating end plate is directly connected to the metallic casing member. In order to increase a mechanical strength therebetween and an air-tightness, it is preferable that the layer positioned on the side of outer radius is provided with a stepped portion. However, two working steps for grinding thereto are required. Futher, when assembling, if a bellows is directly mounted on the layer positioned on the side of inner radius, it is difficult to obtain a satisfactory accuracy of dimension because of thin thickness of the bellows.